In history class, the girl to boy ratio is $5$ to $3$. If there are a total of $32$ students, how many boys are there?
Explanation: A ratio of $5$ girls to $3$ boys means that a set of $8$ students will have $5$ girls and $3$ boys. A class of $32$ students has $4$ sets of $8$ students. Because we know that there are $3$ boys in each set of $8$ students, the class must have $4$ groups of $3$ boys each. There is a total of $12$ boys in history class.